1. Field of the Invention
The present invention relates to a molding resin composition. More particularly, it relates to a saturated polyester base molding resin composition which gives a molded article having improved impact resistance, weld strength, stiffness and mold shrinkage factor.
2. Description of the Related Art
Saturated polyester resins such as polybutylene terephthalate and polyethylene terephthalate have many good properties and are used as materials of, for example, electrical parts, machine parts, automobile parts and the like.
The saturated polyester resin has low notched impact strength and a larger molding shrinkage factor due to its crystallizing tendency. To overcome such defects of the saturated polyestr resin, many proposals have been made. For example, Japanese Patent Publication Nos. 30421/1972 and 25261/1976 disclose addition of an ABS resin to the saturated polyester resin, Japanese Patent Kokai Publication No. 117556/1982 discloses the addition of an AES resin to the saturated polyester resin, Japanese Patent Publication No. 47419/1983 discloses the addition of .alpha.-olefin/glycidyl methacrylate copolymer to the saturated polyester resin, Japanese Patent Kokai Publication Nos. 17148/1983 and 17151/1983 disclose the addition of ethylene/propylene base rubber and .alpha.-olefin/glycidyl methacrylate copolymer to the saturated polyester resin, and Japanese Patent Kokai Publication No. 168750/1985 discloses the use of epoxidized EPDM.
However, none of them can provide a satisfactory molding resin composition since a molded article produced from said composition has only slightly improved notched impact strength, small falling ball strength at a welded part where two or more portions of resin melts meet or intersect with each other in a mold, small stiffness such as tensile strength and flexural modulus, and a large molding shrinkage factor.